In this program we will document the manner of complement activation, histamine release, and activation of coagulation enzymes in three clinical disorders: spontaneously occurring or induced bronchial asthma, reactions to radiocontrast media (RCM), and idiopathic urticaria or angioedema. Specific complement component titrations will be carried out to assess whether the classical or alternative pathways are activated and whether the activation proceeds into the common final pathway. The coagulation system will be analyzed by assessment of fibrin split products. Histamine release will be estimated from serial measurements of plasma levels. In the studies on bronchial asthma, emphasis will be placed on brachial artery blood samples, since our previous studies have shown that arterial, but not venous blood gives significant peaks. In the RCM studies, the purpose will be to determine whether prophylactic therapy with steroids and Benadryl abrogates any of the abnormalities in blood complement, histamine, or coagulation that have been documented previously in untreated patients. In the urticaria/angioedema group, correlations will be sought with presence or absence of immune complexes, and any intrinsic (genetic?) deficiency in one or another of the elements in the complement system sought.